Reflector system for ultrashort electric waves



Sept. 22, 1936. w. DALLENBACH 2,054,895

'. REFLECTOR SYSTEM FOR ULTRASHORT ELECTRIC WAVES Filed Aug. 24, 1953Patented Sept. 22, 1936 PATENT OFFICE REFLECTOR SYSTEM FOR ULTRASHORTELECTRIC WAVES Walter Ditllenbach, Berlin-Charlottenburg, Germany,assignor to N. V. Machinerieen-en Apparaten Fabrieken Meal, Utrecht,Netherlands Atalanta August 24, 1933, Serial No. 686,635 In GermanySeptember 16, 1932 9 Claims.

This invention relates to a reflector arrangement for ultra-shortelectric waves.

It is known already to increase the effect of a parabolic reflector usedfor instance for forming a pencil of rays in conjunction with an emitterfor electromagnetic waves by throwing back to the emitter or to thereflector that portion of the rays emitted by the sender concerned whichdoes not strike the reflector by means of a supplementary reflector. Inthis way energy otherwise lost by stray radiation can be utilized eitherfor stimulating the transmitter or by being added to the usefulconcentrated ray by reflection, which is emitted by the main reflector.

Experiments have shown that an effect similar to that produced by asupplementary reflector can be attained by employing a secondaryemitter, such as an electric dipole, instead of the supplementaryreflector.

It has been proposed to build up such supplementary reflectors fromdipoles arranged at a distance tothe right and left of the axis ofsymmetry of the main reflector. However, this arrangement involvesconsiderable interference with the useful radiation coming from thereflectors. As experiments have proved, a maximum of directional effectand intensity of useful radiation will be attained if, according to theinvention, the secondary emitters are arranged in the shadow of theprimary emitter, i. e., on the axis of symmetry of the reflector.Simultaneously, the use of only one secondary emitter affords theadvantage of simplicity.

By way of example, the invention is illustrated in the accompanyingdrawing, in which Figures 1, 2 and 3 show various embodiments of theinvention in diagram.

Referring first to Fig. 1, l is the primary emitter, an electric dipole,fed by the high frequency circuit 2. The emitter I is disposedapproximately in the focus of a parabolic mirror 3 and producestherefore a more or less bundled ray, as indicated by the boundary lines4. In addition to this ray, a stray ray indicated by the lines 5 is sentforth towards the front by the reflector and lost with respect to theuseful ray 4. Parallel to the primary emitter l and concentrically withrespect to the reflec or axis 6 a secondary emitter I is arranged acertain distance which depends upon the wavelength and is preferablydetermined experimentally by measuring, at a suflicient distance, theintensity of radiation with respect to the reflector axis and,simultaneously, bringing the dipole 1 and the emitter l closer togetherup to the point where maximum intensity of the useful ray is attained.Experiments have proved that the increase in output made possible bysuch an arrangement amounts at least to twice the normal output and, atall events, is greater than the increase that can be effected by asupplementary reflector.

The arrangement according to the invention permits of various changes.It is not necessary to have the dipole l fed by a high frequencycircuit, since the dipole I may also be disposed inside a transmittingtube or valve which itself is located almost in the focus of theparabolic reflector. In this case, owing to the extent of the glassbulb, it is sometimes not possible to bring the secondary emitter closeto the primary emitter so as to insure maximum intensification of theemission, and for this reason it is advisable to dispose both thesecondary and the primary emitters in the bulb of the sending tube.

It is further possible to employ instead of an electric dipole l amagnetic dipole, preferably in the form of a closed circuit.

Another arrangement is shown in Fig. 2 in which a magnetic di-pole 8(closed oscillatory circuit) is provided in the main reflector 3 as aprimary emitter. An electric di-pole I0 is used as a secondary emitter.Both the di-poles 8 and I0 are enclosed in a common vacuum vessel l3. Ifthe circuit 8 represents an oscillatory generator, the secondary circuitcan be brought close to this generator and also at a most suitabledistance with respect to the primary circuit in the case of very shortwaves.

It will be noted that in this embodiment, the axes of the electric andmagnetic di-poles must be disposed perpendicularly to one another, thatis, the axis of the electric di-pole is preferably positioned in theplane of the circuit and perpendicularly to the direction of propagationof the bundled or grouped ray, concentrically with the mirror axis.

Another possibility of combination, not shown, consists in providing anelectric dipole to serve as primary emitter and a magnetic dipoleto actas secondary emitter.

Still another embodiment of the invention provides that instead of theparabolic reflector another reflector arrangement be used which iscapable of influencing the electromagnetic rays coming from the emitterwith respect to extension in space, and particularly of bundling them.Such a reflector system may, for instance comprise a number of electricdipoles disposed parallel to the transmitting electric dipole on aparabolic curve.

parabolic curve l2 extending in a plane vertically to the extent of thedipoles and having as axis the connecting line of the centers from I toI.

In all the arrangements described best effects will be produced if thesecondary emitter is tuned to the frequency of the primary emitter.

The arrangement described in connection with emitters can be usedequally well for receivers.

The invention is of particular interestto the communication artemploying electric waves in the centimeter and decimeter sphere.

1. A system for transmitting or receiving ultra-short electromagneticwaves, comprising a substantially parabolic wave-reflector, a primaryantenna, a reflector antenna consisting of a single wire'tuned to thefrequency of said primary antenna', said primary antenna being disposedsubstantially at the focus of said parabolic reflector and spaced fromsaid reflector antenna a distance substantially equal to one-fourth thewave length, said reflector antenna being disposed on the side oppositethe apex of said parabolic reflector, whereby stray radiation passingfrom the primary antenna is thrown back on said parabolic reflector.

2. A system for transmitting or receiving ultrashort electromagneticwaves comprising a metal reflector designed as a rotary paraboloid, arodshaped primary antenna arranged adjacent the focal pointperpendicularly and symmetrically to the axis of the reflector, and asingle rod-shaped secondary antenna tuned to the frequency of theprimary antenna and arranged parallel to the primary antenna andsymmetrical to the axis of the reflector, said secondary antenna beingspaced from the primary antenna on the side opposite the apex of thereflector a distance less than onefour'th of the wave length whereby thestray ray emitted from the primary antenna is thrown back on saidreflector.

3. A system for transmitting or receiving ultrashort electromagneticwaves comprising a metal reflector designed as a rotary paraboloid, arodshaped primary antenna arranged adjacent the focal pointperpendicularly and symmetrically to the axis of the reflector a highfrequency circuit intersecting the apex of the reflector and connectedto the primary antenna, a single rods' haped secondary antenna tuned tothe frequency of said primary antenna and arranged parallel to theprimary antenna and symmetrical to the axis of the reflector, saidsecondary antenna being spaced from the primary antenna on the. sideopposite the apex'of the reflector a distance less than one-fourth ofthe wave length whereby the stray ray emitted from the primary antennais thrown back on the metal reflector.

4'. A system for transmitting or receiving ultrashort electromagneticwaves comprising a wave reflector including rod-shaped conductorsarranged on a parabolic cylindrical surface, a primary antenna in thefocal line of said reflector, and a single secondary antenna in a planethrough the primary antenna tuned to the frequency of said primaryantenna and spaced from the primary antenna on the side opposite theapex of said reflector a distance less than one-fourth of a planethrough the primary antenna tuned to the frequency of said primaryantenna and spaced from the primary antenna on the side opposite theapex of the reflector a distance less than one-fourth of the wave lengthwhereby the stray ray emitted from the primary antenna is thrown back onthe reflector.

6. A system for transmitting or receiving ultrashort electromagneticwaves comprising a substantially parabolic wave reflectorand a primaryantenna designed as a closed oscillatory circuit, the primary antennabeing disposed adjacent the focal point of the reflector, a singlesecondary antenna in a plane through the primary antenna tuned to thefrequency of said primary antenna and spaced from the primary antenna onthe side opposite the apex of the reflector a distanceless thanone-fourth of the wave length whereby the stray ray emitted from theprimary antenna is thrown back on said reflector.

7. A system for transmitting or receiving ultrashort electromagneticwaves comprising a substantially parabolic wave reflector and a primarythrown back on said reflector.

8. A system as claimed in claim 7 characterized in that said secondaryantenna is arranged inside of said electron tube.

9. A system for transmitting or receiving ultrashort electromagneticwaves comprising a substantiallyparabolic metal'reflector and a closedoscillatory circuit as a primary antenna provided in an electron tubeadjacent the focal point of the reflector, leading-in wires to said tubepassing through the apex of the reflector, and a single rod-shapedsecondary antenna in a plane through the primary antenna tuned to thefrequency of said primary antenna and arranged within the electron tubesymmetrically to the axis of the reflector and spaced from said primaryantenna a WALTER DALLENBACH.

